No, that was Marshall, who was a regular. I believe it was the second to last episode.
Martin Starr (the bearded guy in KU) was in one episode. He was Steven's friend from home who visited him at school.

I fuckin love POA the book but also love POA the movie. POA the movie is the worst HP movie, but the best movie of the four. If that makes sense.
Ever since I started reading the books, I am very disappointed with the movies. Bob, you are in the minority when it comes to the book/movie stuff.

After watching the bonus disc for season 2, I've come to the conclusion that the writers are just making things up as they go. They have no idea what is going to happen, which will be the down fall of the series.
I'll still watch every week.